surface mount technology 0701
TRANSCRIPT
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Advancements in the process of
SMT assembly
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Abstract As the demands of small light camcorder, cellular phones and other
electronic devices have been increased the manufacturing technology used
in the assembling of printed circuit boards has become an important
criterion. Surface Mount Technology is an innovative trend in the field of
printed circuit .This technology reduces size and weight of PCBs. SMT also
provides improved shock and vibration resistance due to lower mass of
components. The smaller lead lengths of surface mount components reducethe parasitic losses and provide more effective decoupling. The usage
automatic machines improved the standards of PCB assembling and then
process became easier and accurate than the through hole technology. In
SMT reflow soldering technique is mostly used now a days. The testing
stage of PCB is the crucial stage. Because of requirement of high density boards we cannot only use normal physical access for testing. So we need to
adopt some new advanced technologies like MDA and boundary scan which
will work in coordination with automated machines in addition.
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Contents What is SMT
Types of SMT
Surface mount component (SMC)
Factors effecting Surface mount design
Types of soldering
Inspection
ICT
Conclusion
References
Learning outcome
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What is SMT A method of constructing electronic circuits in which the components
(SMC) are directly mounted onto the surface of PCBs.
Electronic devices made for this purpose are called surface mount devices
(SMT).And this technique is known as SMT.
In SMT both both SMC and normal THT components are used.
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Types of SMT
Type 1 SMT
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Type 2&3
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Surface mount components
Chip resistors, capacitors
Small outline transistors
PLCC (plastic lead chip carrier)
QFP,SOIC (gull wing)
DIP (dual in line package)
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Factors effecting surface mount designIt depends on a number of factors
Land patterns.
The type of SMT process used.
Packing moisture sensitivity.
Solder joints reliability.
Test nodes.
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Pick and place machine
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Types of soldering
infrared/convective reflow soldering
Wave soldering
Hand soldering
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Reflow soldering machine
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Reflow soldering process graph
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AOI
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ICT
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Boundary scan test
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Conclusion SMT is more advantages than the conventional circuit board. Because it
reduces the size of circuit board, cost, weight etc. And the new automated
machines easier our work and make it more accurate. Due to above
advantages SMT circuit can be mount on the coin or on the postal stamp.
Also the circuit can be mounted on both sides of the circuit board. So now a
days it is used in mobile, calculator or the circuit where small space circuit
is required. But this physical test access does not give accurate results forlatest and some double sided PCBs so we need to adopt latest technology
like boundary scan test access which can detect line faults, short faults and
open faults etc. The AOI machine can work in integration with boundary
scan test access which is very helpful in detecting faults in initial stages
itself.
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References E-BOOK ON SURFACE MOUNT TECHNOLOGYCOMPILED BY DR.
KANTESH DOSS ELCOTEQ, INC.
MIRTEC automatic machines user manual.
www.logextechno.com
Non-Contact Test Access for Surface Mount Technology IEEE 1149.1-1990
www.radioelectronics.com
Surface Mount Technology: Principles and Practice by Ray P. Prasad
The Electronic Packaging Handbook edited by Glenn R. Blackwell